Power terminals are used on devices such as drive units for electric motors. A conventional power terminal tower in a drive unit is often split in two halves where one goes up to the cover and one goes down to the power board and the halves are not on top of each other. Since the electrical signal in the terminal is used on both a control board and a power board both halves are mounted to the control board, which takes up a lot of space on the board, or one of the halves is placed outside of the board and is connected via a bus bar (normally a copper plate) which gives a more expensive solution and a bigger drive. Both solutions give a complicated assembly with many screws, often in inconvenient directions, and they also make the cooling of the terminal worse because of the high thermal resistance to the heat sink. Furthermore these solutions make the cover and the control board tightly tied together and the terminal position cannot be moved on the cover without modifying the one on the control board and vice versa.
Instead of terminals with circular cross-sections some designs use flat plates (bus bars) to take the signals from the outside of the cover and into the boards. One problem here is to achieve a good sealing through the cover combined with robustness and ease of assembly. The use of flat plates often require soldering fixtures in production to keep the bus bars upright, and there can be soldering problems if the boards are slightly bent. To avoid mechanical forces from the outside going all the way down to the solder joints on the board you may want to insert some bends in the plate, but bends are costly because they are often made manually.
Sealing of the area between the power terminal and the cover of the drive unit is important in order to prevent leakage of water etc. into the drive unit. One way of achieving a good sealing is to use O-rings. However, O-ring gaskets that are not rolling often have to be lubricated when mounted into the cover. That is an extra cost and also an extra risk that the lubricant, which often contains oil is misplaced on the surface where the cable shoe is pressed to the terminal with the risk of a bad electrical connection.
Also, gaskets that are not rolling cannot be compressed that much because of the risk that they will get stuck, and they therefore have to be made of harder rubber that demands tighter tolerances on terminal and cover. With a softer rubber gasket the demands on the cover and board tolerances and strength decrease.
When the gasket is rolling there is no need for a groove on the top part of the power terminal, and without that groove the terminal can be die cast with a much simpler casting tool (no slides). The draft on the top of the terminal and the cover has to be there anyway for the cast and molding process. The groove also leaves a parting line from the casting process that has to be removed in order to maintain a good sealing.